Research And Development Of A Miniature Thin-Film Transient Heat Flux Gage

There are a great deal of heat transfer problems need to be resolved in our daily life, science research, aeronautics and space fields, power engineering and so on. With the development of modern science and technology, especially the use of heat transfer in aviation, energy management and so on, it is not sufficient to take the temperature as the only signal of heat transfer. Then, technologies of heat transfer measurement got great development and heat flux gages appeared. Transient heat flux is difficult to be measured in thermal measuring field, and it has not been resolved very well until now. Developing transient heat flux measurement, especially measurement in miniature space has a great significance in energy conservation and aerospace research fields nowadays. A two-dimensional unsteady heat conduction mathematical model is presented. Through this model, factors that can influence measurement precision using surface-mounted transient heat flux gage on heat flux measurement exchanged between low temperature metal board and high temperature gases are simulated. Conclusions can be drawn that changes of the convective heat transfer coefficients can bring errors because of the appearance of heat flux sensors. Furthermore, the changes of the heat flux gages'characteristics can bring measurement errors too. The thinner heat flux sensor is, the larger sensor's dimension is, the tighter the sensor is to be pasted and the smaller thermal conductivity of the measured material is, the higher measurement precision could be and the sooner getting to stabilization could be. Through calculation, there is an optimal length of the dimension, which is about 20mm square. Results of the calculation can provide a reference to manufacture and applications of heat flux gages. Upon comprehensive reviews of the predecessors'results and using thin-film depositing technology, the author developed a thermal-resistant miniature thin-film transient heat flux sensor. A heat flux sensor calibration system is also developed and described in detail in this thesis. Through comparison and calibration experiment analysis, conclusions can be drawn that this calibration system has its advantages and reliability on heat flux gage calibrating. Heat flux sensor is calibrated using this system. Moreover, the test of response has been done using this calibrating system too and the results are compared with predecessors'. All results proved that this heat flux sensor is advanced in response speed, measurement range and dimensions. At last, characteristics of this heat flux sensor are tested through two transient heat flux measurement experiments.